1. Field of the Invention
The present invention relates to a heat treatment apparatus and a heat treatment method for heat treating an object to be processed.
2.Description of Related Art
In the manufacturing of semiconductor devices, various types of heat treatment apparatuses are used to perform heat treatments, such as oxidation, diffusion, CVD, annealing, etc. of objects to be processed, such as semiconductor wafers. Among them, a batch-type heat treatment apparatus, in particular of the vertical type, is known which is capable of heat treating a large number of semiconductor wafers (hereinafter sometimes referred to simply as wafers) at a time. Such a vertical heat treatment apparatus comprises a heat treatment furnace including a processing container having a bottom opening. A holder, loaded with a large number of wafers, is carried (loaded) into the processing container from below, and the wafers in the processing container are heat treated by means of a heating section (heater) provided around the processing container. The heat treatment apparatus is generally provided with a temperature sensor for detecting the temperature of the heater, and a temperature sensor for detecting the interior temperature of the processing container. Based on a signal from each of the temperature sensors, the power of the heater is controlled so that a wafer(s) or the interior of the processing container reaches a set temperature. In this connection, patent document 2 discloses a method in which a follow-up temperature is controlled by interpolating a detection value from a temperature sensor and a set value at a certain ratio in a mixing ratio adjustment section. Patent document 1 teaches provision of a temperature sensor which lies in the vicinity of a wafer and which moves along with the wafer.